Method of making fibrous sheet material



Jam Z3, 1968 P, A. HOMIE-:R ET AL- 3,364,543

METHOD OE MAKING FIBROUS SHEET MATERIAL Filed Dec. l5, 1,965

MfC///Y/Cl COMP/P655 l VE SHR/A019965 caMPREfS/V 5 M/ /V K 46 E ATTORNEYS United States Patent Ofltice 3,364,543 Patented `lan. 23, 1968 ABSTRACT F THE DISCLOSURE A fibrous web, essentially free of impregnating and coating resins and polymers and preferably essentially free of fiber-fiber bonding, having a relatively high density of about .3U-.35 g./cc., and possessing improved propertics for production of leather replacement materials. The web is produced by the process which consists of several steps including forming a fibrous web, and subjecting it to high density needle punching, calendering, lubrication by impregnating with a liquid and mechanical compressive shrinkage.

This invention relates to a dense fibrous sheet having improved and unique properties and to a method of making the same, The fibrous sheet is especially useful for impregnation and coating with polymeric materials in the manufacture of a leather replacement material, and for other purposes.

Leather is composed of a plurality of collagen fibers bound together by reticular tissue which forms a network between the collagen fibers. Therefore, in the manufacture of leather replacement materials, an effort has been made to substitute textile fibers for the collagen fibers and a synthetic polymer for the reticular tissues.

There are certain characteristics of leather which must be reproduced in a leather replacement material. For shoe uppers, which consume more than half of the hides used in the U.S., these characteristics include optimum values of density, relative density, uniformity of density, permeability, roll, break, piping, crease resistance, suppleness, formability (lastability) and dimensional stability to low order stress and strain.

Density is the weight of a given volume of a material and is expressed in grams per cubic centimeter according to the equation.

Density (gm./ce.)=

Weight (ounces per square yard) X133 Thickness (mils) Leather is a dense but supple fibrous material and -it has long been recognized that synthetic leather materials also should be dense and supple, A suitable density is .55 to .70 g./cc.

Relative density is the volume of solid mass in a porous material in relation to the total volume the material oc- A relative density, for example, of .51 indicates a pore space or porosity of .49 (49%). Porosity is the proportion of the volume of a material occupied by interstices. Relative density, together with density, characterizes the degree of compactness of a fibrous sheet structure.

Density uniformity or uniform density- This property relates to the evenness of interstice and fiber distribution within the structure. A method of measuring this property is described in U.S. Patent 2,958,113. In that method a fiber web -is placed between a light source moving in a four-inch line and pulsed at 60 cycles per second and a photocell which feeds its pulsed input into a display cathode ray oscilloscope. The projection of the oscilloscope represents the varying intensity of light as it passes through the batt along its path. The top peaks represent areas of no light transmission through the batt. The bottom peaks denote light transmission through the batt. Non-uniform nature of the batt will be represented by wide fluctuations, particularly in the bottom peaks and widespread between top and bottom peaks. Relatively uniform fluctuations between top and bottom peaks demonstrate uniformity of the product. Relatively narrow spread between top and bottom peaks indicates high covering power.

Another means to determine density uniformity is examination of cross sections of the fibrous sheet under a microscope at about 30 magniflcations.

Preferably a flexible film is coated or laminated to the surface of a fibrous sheet material and the texture and appearance of the coating upon stretching is examined as to the development of irregularities produced by nonuniform density of the fibrous sheet substrate.

Permeability is the ability to allow vapors andliquids to pass through the interstices or pores. It denotes that the interstices of a material are interconnected and are not isolated and sealed olf one from the other as in buoyant foamed polystyrene. Fi-brous sheet materials of up to .75 relative density, i.e. 25% pore space, are extremely permeable to vapors and liquids, provided they are unsaturated or uncoated and possess uniform density. A preferred test method for permeability is described in U.S. Patent 2,723,935.

Roll as related to a flexible sheet material, is the character of its resistance to the rolling or flexure of a near flat bend or crease. It is tested by producing a sharp (small radii) bend of and subsequent flexure of the near flat bend or crease by moving the faces of the folded sheet across one another back and forth in a direction normal to the bend or crease line. Sheet materials with good roll offer even and uniform resistance to the rolling or llexure of a sharp bend or near flat crease. This is most practically evaluated by folding a small sheet of the `material between the extended ngers of both hands and then moving the hands back and forth as when rubbing the palms of the hands together.

Break, as related to a flexible sheet material, is the continuity of structure and appearance of the material on the concave and convex side of a sharp (small radii) bend as it is subjected to flexure as described above when testing or examining for roll characteristics. A marked change in continuity of structure and appearance upon roll testing is considered poor break. When one breaks in a pair of shoes, the appearance of the creases and folds at the instep allows one to judge the break characteristics of the leather or flexible sheet material of the shoe upper.

Piping is a descriptive term also used to denote the degree of structure and appearance of change along the concave line of a sharp (small radii) bend or fold of leather or a flexible sheet'material. This is observed when testing for roll andbreak. The structure of a flexible sheet material is subjected to considerable compressive forces on the concave side of a. sharp (small radii) bend or fold. If the structure collapses, deep creases develop in conjunction with pipelike protrusions of the structure between creases. This is excessive piping and indicates poor roll and break. v

Creuse resistance is the ability of a flexible sheet material or leather not `to collapse or develop deep creases when subjected to the considerable lcompressive forces of a sharp (small radii) bend or fold.

Suppleness is principally considered to be softness or lack of stiffness. Stiffness (or softness) may be tested on a Tinius-Olesen machine in accordance with ASTM 1388- 55T.

Formablty or laszabilty is the ability of a leather or sheet material to be forcibly drawn or stretched into a new configuration without exhibiting the memory -or desire to return to its original configuration as is characteristic of elastic sheet material. An example is the forming of a shoe upper toe from a flat sheet. In order for a material to be formable it must possess a very uniform structure and its components must be able to slip upon each other and assume a stable new configuration.

Dimensional stability to low order stress and strain is the ability of the fibrous sheet material to be rolled and unrolled, saturated with aqueous or solvent saturant systems, heated, coated etc. without excessive elongation, stretching or necking down upon being subjected to the normal tensions of such handling.

Sheet materials ideally suited for shoe upper leather, suede leather, wearing apparel and the like, must possess properties of suppleness, and good roll, and break. Therefore, many solid compositions -of rubber and plastic sheets have been considered as leather replacements because they possess the correct properties of suppleness and drape, roll and break. However, they are not well suited for use as shoe uppers, suede leather, wearing apparel and the like because they do not normally possess the properties of leatherlike feel, permeability, porosity and the ability to draw, las-t, or be formed without memory or desire to return to their original dimension. Non-solid all fibrous .sheet materials like felts or other needle-punched and shrunk materials also have been considered because they possess many of the desirable properties referred to above. They are not suitable themselves, however. Consequently, it has been suggested that they be subjected to saturation or impregnation by a rubber or plastic material, with or without adhesion of the impregnant to the fibrous sheet, in order to obtain all of the properties desired in a shoe upper, suede leather or wearing apparel material.

It has been found that while the leather replacement material containing a fibrous web and a synthetic polymer has properties determined by both materials, the properties of the fibrous web are most influential on the properties of the ultimate product. That is, there has been considerable disclosure of techniques of saturating and/or coating fibrous substrates, followed by finishing processes such as sanding, buffing, dyeing, printing, embossing and the like to render a fibrous sheet suitable for the above-mentioned uses, the choice of which can affect the final product. For example, it has been considered desirable that the impregnant not adhere to the fibers, although, for dimensional stability during processing, it has been necessary to use a resinous bonding agent which does adhere to the fibers, in lieu of a portion of the nonadhering impregnant. However, in spite of the emphasis on impregnation, it has been found that certain properties must exist in the fiber web itself, before any polymer is added.

There has also been consider-ation in the prior art of the preferred density of the fibrous sheet material before and after saturating. It generally has been thought that the density or specific gravity of the unsaturated sheet materials should be from .17 to .2O g./cc. prior to saturation and from .40 to .55 g./ cc. after saturation.

However, it has been found that to provide a fibrous sheet substrate of improved and unique properties, the density prior to saturation should be ..30 to .35 g./cc. or higher, preferably without using feltable scale surface fibers or shrinkage fibers, although `such fibers can be used within the scope of this invention. Utilizing the higher density permits considerable reduction in the amount of saturant -or impregnant required to raise the density of the saturated sheet to the preferred range of .40 to .55 g./ cc. This provides several advantages relating to the fact that the :saturated fibrous sheet exhibits less of the rubbery or plastic properties of the chosen saturant. However, increasing the proportion of the fibers requires that the fiber substrate have more nearly the properties of the ultimate product, since there is less impregnant to correct deficiencies.

Another problem in the manufacture of useful sheet materials for shoe uppers, suede leathers, wearing apparel and many other like products is related to the surface coating. The coating may range from a fraction of a thousandth of an inch to twenty (20) mils or more. It must generally be smooth and exhibit no orange peel or other pattern effect caused by the non-uniform density of the fibrous sheet substrate. (Orange peel is an irregularity in the surface of a coating. Non-uniform density of the fibrous sheet substrate can be one of the causes of orange peel effect in coating. This property or lack of it is judged visually. Visible orange peel effect is considered objectionable in that it is a visible irregularity destroying the uniform appearance of the surface whether embossed finished or not and suggests inferior workmanship or materials.) The same uniform density is required in a noncoated but saturated fibrous sheet where a smooth sanded or buffed surface is required, as for suede leather materials.

Fibrous sheet substrates for saturating and coating heretofore usually have been made without a carrier of the woven yarn type embedded therein because of the pattern effect that it has caused in coatings applied thereto. It has been found, in accordance with one aspect of the invention, that when the fibrous web portion of the sheet has been uniformly compacted without saturant to the density range of .30 to .35 g./cc. or higher, a rather broad choice of woven fibrous yarn materials can be embedded in the fibrous web without causing objectionable pattern effect in the surface of coatings and finishes applied thereto.

In accordance with the present invention, there is provided a fibrous web, essentially free of impregnating and coating resins and polymers and preferably essentially free of fiber-fiber bonding, having the aforesaid higher density of about .3G-.35 g./cc., and possessing improved properties for production of leather replacement materials having the aforesaid characteristics, and a method of making the same. Briefly stated the process consists of several steps including forming a brous web, and subjecting it to high density needle punching, calendering, lubrication by impregnating with a liquid and mechanical compressive shrinkage. A preferred form of the process, illustrated by a fiow diagram in the drawing, consists of carrying out the steps as follows:

(1) Forming the fibrous web from a cardable fiber or a mixture of different kinds of cardable fibers, and introducing a carrier within the fibrous web along the plane of its width and length.

(2) Needlepunching the fibrous web and carrier until the average filament length of the cardable fiber is shortened to change the distribution of the fibers in the fibrous web component from laying in the sheet to a principally random distribution in relation to the length and width and depth of the sheet, and to knit the longer portion of the fiber web filaments to the elements of the carrier.

(3) Kneading and consolidating the fibrous sheet with low order (10 percent or less) planar shrinkage by means of mechanical compressive shrinkage.

(4) Compacting the fibrous sheet by calendering.

(5) Kneading and softening as described in Step 3 to remove the undesirable effects of calendering compaction without loss in density.

(6) Lubricating the fiber surfaces of the fibrous sheet in a liquid bath followed by squeezing, kneading and rcmoval of liquid from the fibrous sheet by saturating in a Suitable liquid bath, mangling, preferably with a hard roll and a soft roll combination, followed by drying the sheet against a smooth surface.

(7) Kneading and consolidating again as in Step 3 to again compact to the desired density obtained after Step 5.

A Wide variety of the fibers and blends of fibers can be utilized in the process, including cellulosic and proteinaceous material fibers and synthetic fibers, for example cotton, wool, rayon, polyolefine, such as polypropylene, polyester, e.g. polyethylene terephthalate, polyamide, such as nylon 66 and nylon 6, acrylics, modacrylics, and the like. An important advantage of the invention is that it is applicable to such a large number of fibers.

The fibers ordinarily will have a denier of about 11/2 to 3 and an initial length of about 11/2" to 2".

The fibers are first formed into a fibrous web. To achieve maximum uniformity of density, the web may be made in a succession of steps. That is, carded fibers may be, for example, air laid in a plurality of webs which then are combined by cross-laying, to cancel some of the non-uniformities in the initial webs. One or m-ore additional webs of the same type may be prepared and laminated to a carrier, and, for convenient operation, one or more of the initial webs may be needle punched to the carrier before one or more additional webs is laminated to it.

The carrier layer is a sheet material having greater dimensional stability than the web and preferably is a woven scrirn, i.e. an open mesh plain woven fabric, e.g. cotton, made of ply yarns, carded or combed, in various Weights and constructions. However, it has been found that the carrier can be composed of a broad range of sheet materials. For example, plastic films also have been used. Ligated or bonded nonwoven webs from a wide range of web forming processes, fibers and bonding agents have also been employed. i

Woven polypropylene scrims and spun cotton yarn scrims are preferred in the practice of the invention, especially when the fibrous sheet is to be used as a substrate for the manufacture of shoe upper, suede leather and wearing apparel materials, although any relatively dimensionally stable, thin sheet material may be used.

Thus, in some embodiments, the carrier may be a lightweight nonwoven fabric or a continuous plastic film such as polypropylene. It also may be possible to omit the carrier in some cases. However, at present a woven carrier is preferred since it improves the stability of the web during high density needle punching and subsequent processing.

The needle punching step produces a high punch density, in the range of 1000 to 5000 punches per inch. The depth of penetration may be varied. As shown by the example described below, very useful results are obtained by punching with deep penetration and then with smaller penetration.

There is considerable published information about preferred needle punching techniques and design of barbed needles to minimize the holes and non-uniform density ordinarily produced by needle punching, to effect entanglement bonding and for densifying fibrous sheet materia-ls, because holes and 4the compacted bundles of fibers produced by needle punching may cause orange peel appearance. However, an important advantage of the present invention is that it has been found unnecessary, in

producing a dense fibrous sheet material, to use special` needles or technique. The well-known Torrington barbed needles are quite suitable. The needleloom and conventional barbed needles are used for increasing density, changing the distribution of the fibers and chopping and shortening the length of the fibrous web staple. Preferably, after needle punching, the mean length of the fiber is to 3A inch with at least about 40% below 1/2 inch and at least about 15% below 1A inch long. For example, the mean length may be 17/32f with 25% below 1A inch length. The needleloom randomly distributes the array of fibers in relation to the width, length and depth of the sheet. Some degree of compaction of the fibrous web is obtained at needleloom if the fibrous sheet is restrained from spreading, e.g. by the carrier. As a result, there is obtained a fibrous sheet exhibiting higher densities with more softness or suppleness than those disclosed by prior art, because of short staple and high density, without necessarily relying on entanglement bond-ing for dimensional stability. Where entanglement bonding is practiced, it has been found that less soft `fibrous sheets are produced and thusranother advantage of this disclosure is that softer fibrous sheets are obtained at higher densities than prior disclosures.

Generally speaking, the lower the denier and the shorter the fiber length in the needled web, the higher the relative density that can be obtained. Therefore, while ranges have been indicated above it is not intended to imply that the advantages of the invention are obtained only with particular values of denier or mean length of lament, although the values given above have been found to give especially good results. Excellent sheets have been made, for example, with one and one-half denier and 17/32 mean length fibrous web components after needle punching.

The web, upon leaving the web forming and needleloom process, has a density in the range of 0.15 to 0.25 g./cc. depending on the type of fiber, needle punches per square inch, denier and mean fiber length of the fibers in the fibrous web. Following this is a series of process steps which densify, improve density uniformity and soften the fibrous sheet. The fibrous sheet with embedded carrier, as it leaves the needle punching step, possesses a moderate degree of uniformity to the extent that, for example, each cube one (l) inch lengthwise by one (l) inch widthwise by the depth or thickness of the sheet has about the same density. However, the fiber distribution of the fibrous web is not uniform to the extent that smaller portions of that cube have uniform density. The fibers have been chopped, shortened in mean length, some are entangled around elements of the carrier, low order surface tufts exist, compacted bundles of fibers exist, and some needle holes exist in the body of the fibrous sheet normal to the surface. The further processing works the sheet and each of its individual component fibers in such a manner that the random positioned bers distribute themselves uniformly, thus developing the uniform den- -sity that is required to prevent orange peel effect in coatings or surface finishes. Furthermore, the fibrous web is compacted to a high relative density which prevents the structural pattern of the carrier from showing in subsequent coatings or surface finishing. All this is accomplished and the softness or suppleness is improved as well.

It will be apparent then that an essential step in the process is the chopping and shortening the.` lament lengths of the fiber to an array of lengths including shorts and longs. This makes possible the achievement of the higher densities in the improved fibrous sheet. The steps following punching add uniformity so that the sheet material possesses a unique combination of properties including high densification, uniform density and softness.

Mechanical compressive shrinkage in accordance with the present invention may be carried out on a compressive shrinkage range of the type referred to in the trade as a double Palmer, since it applies a Palmer finish to the surface(s) of a fabric. This equipment is commoniy employed, eg. for woven fabrics, to provide dimensional stability and prevent further shrinkage in laundering the fabric. As is explained more fully in the American Cotton Handbook (2d ed. 1949) pages 712-716,iit is based on the principle that the shrinkage of say, woven cotton fabrics, in laundering, is caused mostly by mechanical manipulation, and it seeks to prevent subsequent shrinkage by mechanically rearranging the fibers. To this end, the treatment consists of mechanically compressing the fabric in a warpwise direction, usually after it has been softened by moisture.

The fabric ordinarily is moistened, eg. sprayed with water or steam to a low surface pickup, and is laid on an endless blanket as the blanket passes over a roller. Then the fabric travels along with the blanket to an adjoining steam heated drum where it passes between the blanket and the drum. That is, the fabric moves in an S-shaped path over the roller and the drum, being outside of the blanket on the roller and inside of it on the drum. The fabric is compressed as it reverses curvature in passing from the roller to the drum. The path of the fabric around the roller is slightly longer than that of the blanket, but the blanket has a longer path around the drum than the fabric. Consequently, the fabric is compressed lengthwise to t into the reduced lengthwise distance allowed for it as it passes from the roller to the drum. As the fabric passes between the blanket and the drum, the yarn fibers readjust to the compressed shape of the fabric. Further effects are observed because of the nature of the blanket, which may be a pile fabric having, e.g., a wool pile inserted in a Daeron and/r cotton fabric backing having good dimensional stability. As the blanket passes over the roller it is stretched and the tufts tend to lag behind the backing. As the blanket cornes into contact with the drum, the pile is compressed and the tips of the tufts accelerate and ultimately lead the backing. Actually, the tufts slip past the drum just at or below the nip between the roller and the drum. Fabrics laid on the blanket even just above or at the nip are propelled by the accelerating tufts and thereby compressed.

For this action to take place, it is important that the fabric be able to slide against the drum and the drum must be very smooth. If the drum is not smooth, there is no compressive shrinkage. Therefore, it is customary to lubricate the drum with e.g. wax or a silicone. This smoothness, by permitting the fabric to slip over the drum, also irons the fabric.

A double Palmer generally has two drums of this type in line and the fabric is inverted while passing from the first to the second. This permits both sides of the fabric to be ironed. However, it will be appreciated that it is possible to use a mechanical compressive shrinkage machine of the same type having one, three or more such drums in line, each having an associated roller. Since a drum which effects heating will usually be heated by steam under pressure, it is desirable to take suitable precautions to make certain that the drum can withstand the operating pressure. It also is possible to use or omit an auxiliary electric or other type of heating shoe to hold the fabric in the conventional manner as it passes over the roller, if the fabric is not inserted near the nip between the roller and the drum, to use other equipment conventionally employed with a mechanical compressive shrinkage range, or to use any other type of mechanical compressive shrinkage equipment, for example the type disclosed in British Patent 734,587 in which a belt passes over two rollers and is engaged by a third roller which makes a nip with the first of the other two rollers.

In the present process, the compressive shrinkage preferably is carried out at elevated temperatures, for example 250 to 280 F. At least in the first pass through the shrinkage range, and preferably in each pass, the web is fed to the machine under tension. In the first pass, this will stretch it about 2 to 5% of its length. Then the fabric is compressed about 3 to 6% of its length, the net effect being l to 3% compression. In the second and third passes, less tension and less compression are used, because the web has stiffened somewhat. In any event, the compression should not be suicient to introduce corrugations into the surface of the web.

However, a compressive shrinkage range may be adjusted to increase or decrease the linear compressive shrinkage, and useful results are obtained when the sheet receives no net shrinkage. The pressure of the blanket on the sheet material increases its density, without the diiculties associated with calendering. It also works the sheet material to achieve an increase in uniformity of den sity and suppleness and to improve its hand. Preferably, then, there is a net linear shrinkage in the first stage of mechanical compressive shrinkage but none is required in later stages.

It has been learned that by stretching the sheet as it is fed in and utilizing the action of the belts to work the sheet and overcome the stretch, that the iibrous structure is kneaded and blended resulting in marked softening and improvement in fiber-interstice evenness while maintaining or raising density.

The fibrous sheet material is calendered to further increase its density. Fibrous sheet materials can obviously be produced in any density up to solid sheets by applying heat and pressure in a platen press or by high pressure hot calendering. However, in the practice of this invention, the calendered sheet preferably has a density of .30 to .40 g./cc.

It will be appreciated that such pressing action does not improve the density uniformity, tends to pro-duce more dense areas in the sheet near the surfaces in contact with the heated pressure platens or rolls and stiffens the sheet considerably. Therefore, while calendering is useful to increase density, it is employed in combination with other steps which avoid its undesirable effects.

The sheet material is lubricated by thorough impregnation in a liquid bath, which for convenience and economy may be water. Preferably the bath is heated to an elevated temperature in the range of to 212 F. This step generally will result in a low order swelling and loss of some density, compared to the web after the calendering, but is most necessary in order to accomplish uniform aixing and blending of the fibrous components to a uniform density.

The saturated web then is squeezed through a mangle, to remove part of the water. Preferably, the mangle is a pair of rolls one of which is hard, for example steel, while the other is relatively soft and resilient, for example, rubber. This combination further works the bers in their moistened condition to improve uniformity.

Then the web is dried. Suitably the drying is carried out by moving the web over a succession of rotating heated drying cans having polished surfaces, of a type well known in the textile industry. The temperature is, for example, 250 to 280 F., the time of treatment being reduced or increased in relation to the temperature. At this point, the density of the sheet material has been reduced, because of the fiber working. However, uniformity has been improved, and needle holes obscured.

The order of carrying out the foregoing steps may be varied, and a st-ep may be used more than once. Thus, the preferred process illustrated in the drawing subjects the sheet material to mechanical compressive shrinkage three times. However, it is possible to have only one compressive shrinkage treatment, if, for example, the sequence of steps is needle punching, calendering, lubricating and mechanical compressive shrinkage. Therefore, in its broadest sense, the invention is not limited to any particular order of steps although the best results are obtained if certain limitations are observed. These include the use of a lubrication step after the fabric is calendered and a step of mechanical compressive shrinkage after lubrication. The lubrication removes stiffness and surface compacting introduced by calendering without releasing the sheet material to its pre-calendering density; mechanical compressive shrinkage restores density which is lost during lubrication in addition to irnproving density uniformity.

The best results are obtained by using the preferred order of steps, as illustrated by the following example.

A blend of 60% 11/2 denier x 11/2 inch staple length polypropylene and 40% 11/2 denier x 11/2 inch staple length high strength rayon is carded and crosslapped in a conventional manner. The weight of the fibrous web is 4 ounces per square yard. The loose web is fed into a standard needleloom. At the same time a 1.5 ounce per square yard calendered scrim made from fine spun polypropylene is also fed onto the conveyor and the 4 ounce fibrous web is crosslayed on top of the scrim. The web is then needled into the polypropylene scrirn. The needles used in the Hunter Fiber-Locker are conventional ones and supplied by Torrington Company, Torrington, Connecticut and designated No. 77-1172-00-1, dimensions x 18 x 32 x 3RB. The needleloom operates at 600 strokes per minute, giving 230 punches per square inch, the rate through the loom is l0 feet per minute and the needle penetration is 1% inch. Needle penetration is the distance the point of the needle extends below the top surface of the bed plate on the needleloom at the lowest position of the downward stroke.

After the first pass through the needleloom, the sheet is turned over so the scrim is on top. A second 4 ounce web same as above is crosslayed yon the scrim face and needled into it in same manner as above. This gives the structure a weight of 9.5 ounces per square yard. No additional fiber is added in subsequent needleloom passes. The sheet is then needled six additional passes alternating 4one face up then the other. The needle penetration for these passes is s/s, again having a total of 230 punches per square inch per each pass.

Two last passes are made, one on each face, with a reduced needle penetration of M3 inch and again 230 punches per square inch. The two last passes smooths the surface and improves density uniformity. This needling with reduced penetration moves only small amounts of fiber, breaking down or dispersing the large tufts of fiber and filling the large needle holes with small tufts of fiber, yet not penetrating far enough to raise any new large tufts of fiber or creating large holes by deep penetration of the needles. At this point, the fibrous sheet has a gauge of 60 mils and a density of 0.21 grams/cc. The mean length o-f the web fibers is 1%2 inch. The sheet has received a total of 2300 needle punches per square inch.

The sheet is next supplied under tension to a double =Palmer with drum temperature of 250 F. it is initially stretched about 3% and then compressed 5% so that only about 2% planar shrinkage occurs. The gauge is reduced to 55 mils and the suppleness and density uniformity are improved.

The sheet is next calendered at sufcient pressure to reduce the thickness and thus obtain the desired density. This, however, stitfens the sheet and accentuates the nonuniform appearance of the surface because the ultimate density uniformity has not yet been obtained. The thickness at this point is 40 mils and the density is .31 g./cc.

The sheet is next given a second pass through the double Palmer as before, but no further planar shrinkage results. This yields a soft, 4smooth Isurfaced sheet at the desired density of .31 g./cc. However, the needle holes are still discernible and, while the density uniformity is improved, it is not yet to the interstice-fiber evenness desired.

The sheet is next saturated in a water bath at 175 F., squeezed between a chrome plated polished steel roll and a relatively soft (50 durometer hardness) rubber covered roll with a high nip pressure of approximately 4000 lbs. The sheet is then dried on cans. The sheet now has a surface which is very uniform in appearance, the needle entry points are barely noticeable. However, the density is now about 0.28 gram/cc. and slight stiffening has occurred.

The sheet is given a third pass through the double Palmer unit under the same condition as previously in order `to bring the fabric to the desirable density land suppleness. No further linear shrinkage occurs but the fabric is compressed to the correct density of 0.31 gram/ cc. and gauge of 40 mils, has a smooth surface with needle entry points barely noticeable and has a supple, pleasing hand.

It will be appreciated that while detailed examples have been given, various changes may be made without departing from the scope of the invention, as defined in the claims.

What is claimed is:

1. A process for the manufacture of a non-woven textile material which comprises the steps of forming a fibrous web, needle punching the Web sufficiently to reduce the length of the fibers, compacting the web by applying pressure to both of its faces, thereafter lubricating the ber surfaces by saturating said web in a liquid bath and kneading and thereafter consolidating the web by advancing it under tension and subjecting it to mechanical compressive shrinkage.

2. A process for the manufacture of a non-woven textile material as set forth in claim 1 in which the fibers in said web, after needle punching, have a mean length in the range about 3/8 to 3A inch.

3. A process for the manufacture of a non-woven textile material as set forth in claim 1 in which the fibers in said web initially have a denier of about 11/2 to 3 and a length of about 11/2 to 2 inches.

4. A process for the manufacture of a non-Woven textile material as set forth in claim 1 in which said fabric receives about 1,000 to 5,000 needle punches per square inch.

5. A process for the manufacture of a non-woven textile material as set forth in claim 1 including the step of laying at least one said fibrous web against at least one carrier sheet material prior to needle punching, and in which the fibers in said web are needle punched to said carrier sheet material, whereby the dimensional stability of said web is increased.

6. A process for the manufacture of non-woven textile material as vset forth in claim 5 in which said carrier sheet material is a woven scrim, the densification of said web during said process preventing said scrim from causing surface irregularities.

7. A process for the manufacture of a non-woven textile material essentially free of impregnating and coating resins and polymers which comprises the steps of forming at least one fibrous web of fibers,

needle punching at least one said web to at least one layer of a carrier sheet with a needle density of about 1,000 to 5,000 punches per square inch, and until the fibers are shortened, and to increase the density of the web to about 0.15 to 0.25 g./cc., kneading and consolidating by advancing the web under tension sufficient to stretch it about 2 to 5% of its length and subjecting the web to mechanical compressive shrinkage to reduce its length about 1 to 3%,

calendering the web to increase its density to about 0.30 to 0.40 g./cc.,

kneading and consolidating by advancing said web under tension and subjecting the web to mechanical compressive shrinkage, lubricating said web by saturating it with water heated to about 170 to 212 F., squeezing the web in a mangle comprised of a hard metal roll and a resilient rubber roll and drying the web while in contact with a moving surface heated to about 250 to 280 C., and

kneading and consolidating by advancing 'said web under tension and subjecting said web to mechanical compressive shrinkage.

8. A process for the manufacture of nonwoven textile material as set forth in claim 1 in which said `web is compacted by calendering.

9. A process for the manufacture of nonwoven textile material as set forth in claim 1 in which said liquid bath comprises heated water.

10. A process for the manufacture of nonwoven textile material as set forth in claim 1 including the steps of squeezing said web to remove said liquid after lubrication and then drying it.

11. A process for the manufacture of nonwoven textile material as set forth in claim in which said fabric is squeezed in a mangle comprising a hard roll and a resilient roll and dried in contact with a moving heated surface.

12. A process as set forth in claim 1 in which the tension under which said web is advanced is sufficient to stretch it.

13. A process for the manufacture of an unbonded nonwoven textile material which comprises the steps of forming at least one fibrous web of fibers having a length of 11/2-2 inches and a denier of 11/2 to 3,

needle punching at least one said web to at least one layer of woven scrim with a needle density of about 1,000 to 5,000 punches per square inch, and until the bers are shortened to a mean length of about 3/s to 3A inch with at least about 40% shorter than 1/2 inch and at least about 15% shorter than 1A inch, and to increase the density of the web to about 0.15 to 0.25 g./cc., kneading and consolidating by advancing the web under tension suflicient to stretch it about 2 to 5% of its length and subjecting the web to mechanical compressive shrinkage to reduce its length about 1 to 3%,

calendering the web to increase its density to about 0.30 to 0.40 g./cc.,

kneading and consolidating by advancing said web under tension and subjecting the web to mechanical compressive shrinkage, lubricating said web by saturating it with water heated to about 170 to 212 F., squeezing the web in a mangle comprised of a hard metal roll and a resilient rubber roll and drying the web while in Contact with a moving surface heated to about 250 to 280 C., and

kneading and consolidating by advancing said web under tension and subjecting said web to mechanical compressive shrinkage.

14. A process as set forth in claim 13 in which said bers are a blend of polypropylene and rayon.

15. A process for the manufacture of a nonwoven textile material essentially free of impregnating and coating resins and polymers which comprises the steps 0f forming at least one fibrous web of fibers having a length of 11/2-2 inches and a denier of 11/2 to 3,

needle punching at least one said web to at least one layer of a carrier sheet with a needle density of about 1,000 to 5,000 punches per square inch, and until the fibers are shortened to a mean length of about Vs to 3A inch with at least about 40% shorter than 1/2 inch and at least about 15% shorter than 1A inch, and to increase the density of the web to about 0.15 to 0.25 g./cc., kneading and consolidating by advancing the web under tension sufhcient to stretch it about 2 to 5% of its length and subjecting the web to mechanical compressive shrinkage to reduce its length about 1 to 3%,

calendering the web to increase its density to about 0.30 to 0.40 g./cc.,

kneading and consolidating by advancing said Web under tension and subjecting the web to mechanical compressive shrinkage, lubricating said web by saturating it with water heated to about to 212 F., squeezing the web in a mangle comprised of a hard metal roll and a resilient rubber roll and drying the web while in contact with a moving surface heated to about 250 to 280 C., and

kneading and consolidating by advancing said web under tension and subjecting said web to mechanical compressive shrinkage.

References Cited UNITED STATES PATENTS 2,881,505 4/1959 Hoffman 28-72.2

FOREIGN PATENTS 990,689 4/1965 Great Britain.

LOUIS K. RIMRODT, Primary Examiner. 

